The present invention relates to disposable absorbent articles comprising microporous polymer films. More specifically, the present invention relates to disposable absorbent articles comprising microporous polymer films that are particularly suitable for the printing of registered graphics thereon.
Polymeric materials provided in the form of films or sheets have been used in a variety of commercial products, including diapers, feminine care products, adult incontinence products, and the like. In the manufacture of disposable absorbent articles, such as diapers, microporous polymer films have generally been incorporated into the structure of the article as a part of the layers that are positioned away from the wearer""s body during use (often called xe2x80x9cthe backsheetxe2x80x9d). The backsheet provides a liquid impervious barrier so that exudates absorbed and contained in the absorbent core of the article are prevented from leaking, and particularly so that urine stains outside the diaper are prevented.
A nonwoven material is often laminated or otherwise adhered to a microporous polymer film to form the backsheet of a disposable article. The nonwoven material provides the appearance of cloth and a cloth-like feel on the outside of the garment such that wearers and caregivers perceive a garment-like comfort. The combination of a nonwoven material and a microporous film is suitable for disposable absorbent articles such as diapers, including pull-on type and tape-type diapers, feminine care products, and adult incontinence products. An exemplary pull-on type disposable diaper, which is put on by inserting the wearer""s legs into the leg openings and sliding the garment up into position about the lower torso, is disclosed in Buell U.S. Pat. No. 5,569,234, xe2x80x9cDisposable Pull-on Pantxe2x80x9d.
For disposable absorbent articles, especially disposable diapers, it is also often desired to provide graphic designs on the articles to enhance their appearance and their consumer acceptance. In previously known articles, the nonwoven layers have typically been printed with such graphic designs. This is because the printing process for nonwoven materials is typically easy to control, because the surfaces of such materials tend to provide stronger mechanical, properties that make them more amenable to printing. See, e.g., EP Publication No. 0 604 729; Yeo U.S. Pat. No. 5,503,076; Schleinz U.S. Pat. No. 5,458,590. However, high resolution, multi-color registered graphics, which are consumer-preferred, usually cannot be printed on such materials. Thus the quality of the graphics that can be printed upon nonwoven materials is typically much lower than that which can be achieved by printing upon microporous film.
Microporous polymer films provide excellent surface characteristics that make them suitable for the printing of high resolution graphics. However, the existing microporous polymer films, see, e.g., Japanese Laid-Open Patent App. (Kokai) No. 9-25372, are not mechanically stable enough to support the printing of the high resolution, multi-color registered graphics that are consumer-preferred. This is due in large part to their thermal instability. The thermal shrinkage associated with existing microporous materials has made it difficult to exploit their ability to support the application of high resolution graphics.
It has also been found that a high degree of whiteness, i.e., the visual appearance of the white color of the article as seen by the consumer, is very important to the consumer. Consumers tend not to accept articles that incorporate films having a yellowish or off-white shade. In addition, breathability, the ability of the article to allow water vapor to escape, is important for wearer comfort and for consumer skincare acceptance. A lack of breathability may result in a hot, stuffy, skin-unfriendly product for the wearer.
Based on the foregoing, there is a need for disposable absorbent articles comprising a microporous polymer film that is mechanically stable enough to support the printing of high resolution, multi-color registered graphics, while also providing breathability and a high degree of whiteness. None of the existing absorbent articles provides all of the advantages and benefits of the present invention.
The present invention is directed to a disposable absorbent article comprising a topsheet, a backsheet and an absorbent layer between the topsheet and the backsheet, wherein the backsheet is comprised of a microporous polymer film printed with a registered graphic and comprising by weight: from about 30% to about 60% of a polyolefin; and from about 40% to about 80% of calcium carbonate; wherein the film has a xe2x80x9cbxe2x80x9d value between about 0 and about 0.5 and exhibits less than about 2% thermal shrinkage at about 50xc2x0 C. and about 50% relative humidity for one week.
These and other features, aspects, and advantages of the invention will become evident to those skilled in the art from a reading of the present disclosure.